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I've read a LOT of threads about bleeding rear brakes and heard all kinds of tricks to get it accomplished - including installing a larger master, pushing fluid, etc... I finally figured it out.

Normally I use a hand vacuum pump with a fluid chamber to bleed brakes, until it becomes a slow process and then I pull out an A/C vacuum pump to pull a vacuum through the bleeding chamber for me. That didn't help very much this time, so I started exploring. Since I had replaced all the hoses, I knew there was LOT of air in the system. The first thing I did was remove the bleed screw, wrap 2 wraps of Teflon tape around the threads so they don't suck tons of air, and reinstall it half way.
I clamped off the right side low pressure hose (above the rear axle) and started pulling a vacuum on the LH side. Then I went around to the reservoir to make sure it was full (and it was) and I could hear the vacuum pump sucking air from it!!! I grossly overfilled the reservoir, and the gurgling stopped. Bleeding immediately improved, and all the air came out in a matter of seconds. Bingo!!! I switched to the other side and pulled a vacuum on that side with the LH hose clamped off, bleeder threads wrapped in Teflon. Bingo again!!! I instantly had good pedal pressure. I also had a leak from the RR caliper seal that was bad, another matter altogether.

The lesson here: grossly overfill the rear half of the reservoir before bleeding, and keep it overfilled until the master cylinder has pressure. Then bleed down the high pressure side, which will rectify the overfilled system. I plan to keep it on the side of slightly overfilled, just to keep air from entering the master again!!!
 

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Yes - Thanks. It's always a problem bleeding the low pressure rear brakes, even with the 3/4" master cylinder.


It would be worth cutting and pasting this into the "Solutions and DIY Articles" forum.
 
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